It is known that some cosmetic compositions such as blushers, eye shadows, face powders or foundations, are provided in the form of compacted or cast powders. These are anhydrous compositions called "compact powders", (or "compacts") mainly consisting of a mixture of coloured or non-coloured powders and a fatty binder (oils or mixture of oils and waxes), and shaped by compression, or by casting into a container serving as mould. These powders are generally used by removing a small quantity of powder and then applying to the skin by means of an applicator (sponge, powder puff or brush).
The preparation of binding agents in such compact powders involves many problems. The final product should be sufficiently homogeneous and compact in order to avoid the fragmentation caused especially by impact, while retaining a good disintegration capacity. Moreover, the composition should have a smooth feel and should be easy to spread in a continuous manner. In addition, the binder should be compatible with pigments, and specialists know the problems of degradation of certain pigments when conventional fatty binders are used.
It is known, moreover, that certain make-up compositions are provided in the form of powders called "loose powders", in which the particles are neither compacted nor dispersed in a fatty continuous phase, but retain on the contrary their individuality. Such loose powders often contain a fatty substance (oil) whose role is especially to increase the smoothness of application to promote the adherence of the powder to the skin, and to allow solubilization of some active ingredients. Some loose powders may contain relatively high quantities of oil without the particles having a tendency to agglomerate. Such is the case especially for powders containing particles in the form of hollow microspheres made from synthetic thermoplastic materials see especially Patent EP-0,254,612. But the formulation of such loose powders poses the problem, which is already mentioned above, of the degradation of certain pigments in the presence of the fatty substances conventionally used.
In the present application, the expression "fatty binder" denotes a fatty substance or a mixture of fatty substances constituting the binder for the compacted or cast powders as well as a fatty substance or mixture of fatty substances present in the loose powders especially for increasing the smoothness of application and promoting the adherence to the skin.
The use, as binding agents, in a compacted powder, of silicone oils, which are low-viscosity linear polysiloxanes (polydimethyl siloxane or analogue, abbreviated PDMS), in combination with high-viscosity PDMS compounds (silicone gums), is described in Patent Application JP-61-180707.
The use, as binders, of silicone resins (three-dimensional polycondensation products), in combination with volatile silicones, in cosmetic powders has also been recommended; see for example Patent Applications JP-61-065809, JP-61-161211 and JP-62-298512.
Anhydrous cosmetic compositions containing coated pigments, dispersed in a PDMS-based binder, optionally in combination with a substituted linear polysiloxane (silicone wax), with a cyclic polysiloxane and/or with a conventional wax, have been described in Patent Application EP-133 963. The pigments are coated by chemical bonding with a polysiloxane in order to allow their dispersion in the binder.
A study of these various constituents has shown that low-viscosity silicone oils, mixed with silicone gums, are useful because they confer, especially on the composition, properties of smoothness, ease of spreading and homogeneity. But the make-up behaviour properties and the fallimpact resistance properties of the compact are poor.
Polysiloxane waxes make it possible to obtain a good ease of spreading and an acceptable homogeneity of the make-up and improve the mechanical properties (resistance to fallimpact). But the behaviour properties are not satisfactory.
Silicone resins confer good behaviour and fall-impact resistance properties, but the compositions lack smoothness.
It should be noted that the combination of two classes of silicone binders generally does not bring about notable improvement of the properties.
Accordingly, the addition of a silicone resin to high- and low-viscosity PDMS compounds reduces the ease of spreading, whereas, separately, the two constituents give compositions which are easy to spread. Likewise, the homogeneity individually provided by the two constituents deteriorates when they are combined. On the other hand, the behaviour is improved.
The addition of a low-viscosity silicone oil to a silicone resin does not improve the smoothness and notably reduces the ease of spreading and the homogeneity.
It has now been discovered that the combination of three classes of silicones (oils, waxes and resins), optionally combined with silicone gums, in the preparation of the fatty binder, makes it possible to obtain powders whose cosmetic properties as a whole are improved or maintained at a very satisfactory level. In addition, such a binder is compatible with all the pigments used in cosmetic powders, including easily degradable mineral pigments such as manganese violet or chromium oxides. Furthermore, the binder conforming to the invention does not require the coating of the pigments in order to facilitate their dispersion.